1. Field of the Invention
The present invention relates to an apparatus which records an image on a recording sheet by causing recording particles to jump and then directly depositing the particles on the recording sheet such as a paper sheet.
2. Description of the Related Art
A recording apparatus is disclosed in U.S. Pat. No. 5,477,250. The recording apparatus has a rotatable cylindrical toner carrier which holds charged toner particles on the outer peripheral surface thereof, and a back electrode which is disposed with a gap from the toner carrier. The back electrode is electrically connected to a power source to form an electric field which electrostatically attracts the charged toner particles on the toner carrier toward the back electrode. An insulating plate having a plurality of apertures through which toner particles can pass is placed between the toner carrier and the back electrode. The insulating plate has annular electrodes which surround the apertures, respectively.
In the recording apparatus, when a voltage corresponding to an image data is applied to one of the electrodes, the toner particles in a position on the toner carrier where is opposed to the electrode are peeled off to jump into the corresponding aperture. The toner particles which have passed through the aperture are deposited on a recording sheet to form a dot. An image corresponding to the image data is recorded on the recording sheet by a mass of such dots.
In the recording apparatus, a cluster of toner particles which jump from the toner carrier is dispersed during a period when the toner particles pass through the aperture, and hence a dot formed on the recording sheet has an obscure outline and a low density. As a result, there arises the problem in that a formed image lacks sharpness. In order to solve the problem, a method has been proposed in which a converging electrode is disposed in the periphery of the aperture in the insulating plate and on the side of the back electrode with respect to the annular electrode, a constant voltage of the same polarity as that of the charged toner particles is applied to the converging electrode, and a cluster of toner particles which pass through the aperture is inwardly converged in a radial direction by an electric repulsive force, whereby a dense dot having a sharp outline is formed on the recording sheet.
However, a recording apparatus provided with such a converging electrode has the other problem in that the jumping toner particles are accelerated by an electric field formed between the converging electrode and the back electrode, and the toner particles are scattered by an impact at the collision with the recording sheet, whereby the image quality is deteriorated.